In designing loudspeaker systems, two important concerns are the vertical and horizontal directivity of sound radiation from the system. For example, a certain class of acoustical horn is known for taking acoustic power from a vertically oriented transducer and redistributing that power in a generally wide horizontal pattern, where it is most useful, i.e., to the ears of a listening audience in front and horizontally to the sides of the loudspeaker system. Redistribution of acoustic power in this manner comes at the expense of distortion due to deformation of the spherical wave front that is initially generated by the transducer. It is a goal of acoustical horns to provide optimal directivity of acoustic power with a minimum of distortion over the desired spectrum of acoustic wavelengths.
The design of this type of acoustical horn has been driven by a ray-tracing paradigm. The prior art shows that designers have treated acoustic power as emitting from the transducer as a plurality of linear rays, and the design of these acoustical horns has been based on providing desired directivities to these linear rays. As one example, U.S. Pat. No. 4,836,329 to Klayman teaches an acoustical horn including concave and convex conical sections defined by sweeping a single line segment 180° with the axis of rotation lying midway along the line segment. The design is intended to operate so that any “ray” of acoustic power emitting from the transducer proceeds in a straight line until contact with a surface of the horn, at which point the ray is redirected based on its angle of incidence in a straight line out of the horn.
One consequence of this in prior designs was rigid constraints on the geometry of the horn and its surfaces. This reduced the ability of horn designers to customize the horn for different uses and for different transducers, for example a compression driver versus as domed tweeter.
It has been determined that treatment of acoustic power from common transducers as a set of linear rays traveling through air is fundamentally flawed, as well as conceptually misleading. Acoustic power in fact emits from a transducer in spherical waves, which expand in a sphere outward from the transducer into the surrounding environment. Given this recognition, there is a need to reconsider the approach to designing an acoustical horn with reflective surfaces of this type (Klayman et al), optimally suited to shape and direct spherical waves as opposed to rays.